Multiple jet aerator module

ABSTRACT

A multiple jet aerator module or header which is formed substantially completely of fiber glass and which includes a right-circular tubular sheet-form liquid duct and a rightsemicircular tubular sheet-form air duct having a radius substantially less than the radius of the liquid duct. Molded fiber glass liquid nozzles are located along the length of the liquid duct and a corresponding number of liquid-air nozzles are located along the length of the air duct in register with the liquid nozzles.

United States Patent [191 Mandt MULTIPLE JET AERATOR MODULE [75] lnventor: Mikkel G. Mandt, Prophetstown, Ill.

[73] Assignee: Houdaille Industries, Inc., Buffalo,

[22] Filed: Nov. 8, 1973 [21] Appl. No.: 413,824

[52] US. Cl. 239/177; 210/7; 210/272; 210/273; 239/226; 239/291; 239/424; 239/254 [51] Int. Cl E03c 1/084; B05b 3/12; BOSb 7/32 [58] Field of Search 239/177, 251, 254, 226, 239/248, 291, 296, 418, 398, 423, 428.5,

[56] References Cited UNITED STATES PA ENTS 506,879 10/1893 Jewell 210/272 X 2,843,153 7/1958 Young 138/55 3,077,240 2/1963 Betts 181/61 X 3,220,506 11/1965 Vernet 181/61 X [[1 3,897,000 [451 July 29,1975

3,587,975 6/1971 Moffett 210/272 X 3,733,263 5/1973 Mandt 210/7 FOREIGN PATENTS OR APPLICATIONS 419,325 ll/l934 United Kingdom 239/254 Primary ExaminerR0bert S. Ward, Jr. Attorney, Agent, or Firm-Hill, Gross, Simpson, Van Santen, Steadman, Chiara & Simpson [57] ABSTRACT A multiple jet aerator module or header which is formed substantially completely of fiber glass and which includes a right-circular tubular sheet-form liquid duct and a right-semicircular tubular sheet-form air duct having a radius substantially less than the radius of the liquid duct. Molded fiber glass liquid nozzles are located along the length of the liquid duct and a corresponding number of liquid-air nozzles are located along the length of the air duct in register with the liquid nozzles.

17 Claims, 7 Drawing Figures PATENTEB JULZQIBYS 3 897, 000

MULTIPLE JET AERATOR MODULE BACKGROUND OF THE INVENTION This invention relates generally to the field of waste liquid treatment in which air or other oxygencontaining gas is introduced into waste liquid to reduce the biochemical oxygen demand thereof. More specifically, the invention relates to a multiple jet aerator for adding air or oxygen to the waste liquid being treated. Although the term air" will be used from time to time in the description to follow, it should be understood that the invention is sufficiently broad to encompass the use of any oxygen-containing gas, including, but not limited to air.

There are a variety of well known liquid treatment processes and systems which require or depend upon the introduction or transfer of oxygen into the liquid for purification purposes, or more specifically for the purpose of reducing the B. O. D. (biochemical oxygen demand) of the liquid. For example, one of the most widely used systems for treating sewage, the activated sludge system, depends in large measure upon the introduction of oxygen into the sewage to reduce B. O. D. thereof to acceptable limits.

There are also a variety of well known methods and systems for introducing oxygen into the liquid to be treated. One of the simplest and, in terms of operating costs, least expensive, involves merely the retention of the waste liquid in a pond or tank or the like which is open to the atmosphere. Some of the oxygen from the air will be transferred into the waste liquid and ultimately reduce the B. O. D. thereof, but it will be appreciated that this involves an extremely slow process and is not generally feasible, particularly in heavily populated metropolitan areas in which the capacity of the waste treatment system must be great.

Another method for reducing the B. O. D. of the waste liquid involves the retention of the liquid in a pond or the like and introducing air or oxygen under pressure through a tube or diffuser or the like directly into the waste liquid below the surface thereof. While this system increases the rate at which the B. O. D. is reduced, it does involve operating costs in the form of horsepower consumption for the air fans or compressors or the like.

Another method which has been used in the past in volves large rotary brushes which are partially submerged in the liquid and which are slowly rotated so that the brushes themselves ultimately rise out of the liquid into the atmosphere and entrain air, and then descend into the liquid, whereupon a portion of the entrained air is transferred into the waste liquid. This sytem also involves substantial consumption of power and in addition requires one or more large rotating mechanical brushes which are subject to deterioration and wear of moving parts after prolonged periods of use.

It has been determined that one of the most sufficient methods of introducing air into the waste liquid involves the use of jet aerotors which employ the venturi principle. In this latter method the liquid is pumped through a high velocity liquid jet nozzle, thus generating a reduced pressure on the discharge side of the nozzle. A mixing chamber or zone surrounds the discharge of the liquid nozzle and is communication with the atmosphere, either directly or indirectly through an air compressor. The high velocity liquid jet which is discharged from the liquid nozzle mixes with or entrains the air in the mixing zone and the air and liquid are then discharged through a liquid-air nozzle directly into the waste liquid below the surface thereof.

In terms of the oxygen-liqiud transfer, this latter system involving jet aerators produces greater efficiency than the aforementioned systems. Thus the concept of introducing air or oxygen into the waste liquid by means of jet aerators is particularly attractive in terms of system capacity, efficiency, and operating costs.

Jet aeration principles have, in fact, been utilized in a number of installations involving waste liquid treatment. including activated sludge systems in which the introduction of the air or oxygen into the waste liquid is accomplished in what has been generally referred to as an aeration tank. The jet aerators which have been utilized in such installations have been formed of metal. generally a machined casting made of bronze or the like. Such generators, while efficient in terms of gasliquid transfer, are rather expensive to manufacture and thus the initial cost of jet aeration systems utilizing jet aerators has been relatively high vis-a-vis some of the other well known aeration systems.

In one type of jet aeration system, for example, in which banks ofjet aerators have been arranged at intervals around an aeration tank each of the jet aerators constitutes an individual device and thus if, for example, the required capacity of the aeration system is such to necessitate the use of 20 or 30 jet aerators of a given size, each must be individually manufactured. The initial cost of such a large number of jet aerators has in many instances reduced the applicability or feasability of jet aeration systems, notwithstanding the enhanced operating efficiencies derived through the use of such systems.

The present invention addresses itself to a reduction in the initial cost of jet aeration systems and in many respects improves upon the performance of such systems, not only by virtue of the materials involved in the manufacture of the jet aerators but also by virtue of the configuration thereof.

SUMMARY OF THE INVENTION The present invention may be summarized as comprising a multiple jet aerator module which is formed from a number of components into a unitary structure which embodies not only a plurality of jet aerators but also a liquid duct as well as an air duct for conducting waste liquid and air to the jet aerators. In a preferred embodiment the liquid and air ducts are formed of light weight filament wound fiber glass and the liquid and liquid-air nozzles are formed of molded fiber glass. The method of fabricating the unitary structure is also involved in the present invention, as a consequence of which the cost of fabrication is substantially less than the cost of manufacturing an equal number of previously known individual jet aerators, along with the liquid and air manifolds which interconnect the jet aerators.

From a first cost point of view, the present invention renders a jet aeration system comperable to the previously known, less efficient aeration systems, and as a consequence combines the high airliquid transfer efficiency of a jet aeration system with the relatively low initial cost of the previously known aeration systems.

BRIEF DESCRIPTION OF THE DRAWING F IG. 1 illustrates diagrammatically a top plan view of an aeration tank, a so-called oxidation ditch or the like equipped with a pair of multiple jet aerator modules constructed in accordance with the principles of the present invention.

FIG. 2 is a top plan view of one of said multiple jet aerator modules.

FIG. 3 is a front view of the jet aerator module shown in FIG. 2.

FIG. 4 is an end view of the jet aerator module as viewed along the lines IV-IV shown in FIG. 3.

FIG. 5 is a cross sectional view taken along the lines VV shown in FIG. 3.

FIG. 6 is a side elevational view of a liquid-air nozzle of the present invention.

FIG. 7 is a side elevational view of a liquid nozzle of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is illustrative of an aeration tank or oxidation ditch or the like in which is confined a quantity of waste liquid to be treated. The tank, which is indicated at reference number 10, is illustrated as being circularly shaped in top plan view but it should be appreciated that the configuration of the tank or ditch 10 shown in FIG. 1 is merely examplary. The tank or ditch may take other forms, need not be circularly or cylindrically shaped and in some instances may be oblong and take on the appearance of a race track when viewed from above.

Residing within the tank 10 and submerged below the level of the waste liquid confined therein are a pair of multiple jet aerator modules, indicated at reference numerals 11, both of which are constructed in accordance with the principles of the present invention. The modules l1, l1 may be identical in form and in the illustrated embodiment are positioned in a manner to promote the flow of the waste liquid in the tank 10 in a counterclockwise direction. As will be appreciated and understood by those skilled in the art, one of the advantages in disposing the modules in the manner illustrated is to produce or generate movement of the waste liquid, thereby maintaining any settleable solids that may be contained in the waste liquid in suspension.

Referring to FIGS. 2 and 3, each of the modules 11 may be characterized as comprising a unitary elongated or axial structure, along the length of which are located in space relation a plurality of liquid-air nozzles, as indicated at reference numerals 12. A pair of flanges 13, 13 are provided at the opposite ends of the module 11 to receive a pair of end caps 14, 14, which may be secured to the flanges 13, 13 by any suitable fastening means such as the bolts indicated at reference numerals 16 in FIG. 4.

Extending forwardly from one end 17 of the module 11 is a conduit 18 for delivering air or other oxygencontaining gas from a supply conduit 19 to the module 11. Extending downwardly from an opposite end portion 20 of the module 11 is a conduit 21 for supplying pressurized waste liquid to the module 11 from a supply conduit 22.

Referring to FIG. 5, the unitary structure which comprises the multiple jet aerator module 11 is formed of several components, one of which is a cylindrically shaped member 23 which forms the waste liquid duct or manifold for servicing the various liquid-air nozzles 12. The liquid duct 23 is essentially tubularly sheetform in configuration and in the preferred embodiment is made of light weight filament wound fiber glass. The liquid duct 23 preferably extends in one piece the entire length of the module 11 and is initially formed by known manufacturing methods utilizing filament would fiber glass of solid wall construction, no provision being initially made for the liquid-air nozzles 12.

A second member comprises an air duct 24 which is also formed of light weight filament wound fiber glass. The duct 24 also preferably extends the entire length of the module 11 and is initally constructed of tubular or cylindrical configuration and then split or cut along the length thereof to provide the light-semicircular cylinder as shown in FIG. 5. The method of forming the air duct 24 from a right circular cylinder which has been divided into two identical right-semicircular cylinders provides the added advantage of being able to form two air ducts 24 for two of the modules 11 from a single fiber glass cylinder.

The radius of the air duct 24 is less than the radius of the liquid duct 23 and in the preferred embodiment the radius of the former is approximately two-thirds the radius of the latter to provide a tear drop configuration in cross section for reasons which become more apparent hereinafter.

The air duct 24 is bonded to the outer surface of the liquid duct 23 by means of any suitable bonding material such as epoxy resin or the like as indicated at reference numerals 26. The resin bond may comprise a dead or weld running along the entire length of the liquid duct 23 to provide not only an exceptional air-liquid seal but also to provide a very secure and rigid affixation between the liquid and air ducts 23 and 24.

Before the air ducts 24 is secured and bonded to the liquid duct 23 a plurality of longitudinally spaced radially aligned bores as indicated at reference numeral 27, are formed in the liquid ducts 23 to receive a corresponding plurality of liquid nozzles as indicated at reference numeral 28. As shown in FIG. 7, the liquid nozzles 28 are provided with a flange portion 29 which, in side view, conforms to the shape of the walls of the liquid duct 23. The flange portion 29 comprises an outer wall surface 30 which conforms to the configuration of the bore 27 formed in the wall of the liquid conduit 23.

The liquid nozzles 28 are also securely fastened to the liquid ducts 23 and may preferably be bonded thereto by means of resin as discussed above in connection with the bonded connection 26.

After the liquid nozzles 28 have been mounted on the liquid duct 23 and the air duct 24 has been secured to the outer wall surface of the liquid duct 23 a plurality of bores as indicated at reference numeral 31 are formed in the air duct 24 and register with and in concentric relation to the bores 27 formed in the liquid duct 23 and the liquid nozzles 28 mounted thereon.

A liquid air nozzle, as indicated at reference numeral 12, is then mounted on and bonded to the air duct 24 at each of the bores 31. Once again, the preferred embodiment utilizes a resin for the purpose of securing and bonding the liquid-air nozzles 12 to the air duct 24. In an alternative arrangement, the liquid air nozzles, instead of being entirely smooth-walled, may be provided with an end flange 32 as shown in FIG. 6. The provision of the flange 32 and the abutment thereof against the inner wall of the air duct 24 provides a stronger fastening connection by virtue of the fact that the resin bonding material may cover an entire forward wall surface 33 of the flange 32, rather than merely a narrow banded portion of the outer periphery of the liquid nozzle 12. If the flange 32 is utilized then, of course, the liquid-air nozzles must be secured to the air ducts 24 before that duct is secured to the liquid duct 23, since the outer dimensions of the flange 32 exceed the diameters of the bores 31. v

After the entire assembly comprising the liquid ducts 23, the air duct 24, the plurality of liquid nozzles 28 and the plurality of the liquid-air nozzles 12 are all secured together bonded to provide a unitary structure the entire assembly is covered with a layer of filament wound fiber glass as shown in reference numeral 34. This outer layer 34 of fiber glass so totally and completely combines and secures the air duct 24 to the liquid duct 23 that the strength and rigidity of the entire module 11 is at least as great as would be if the entire structure were molded as an integral or monolithic structure.

In addition to the previously mentioned advantages of the multiple jet aerator module 11 over the previously known individual jet aerators, other advantages are most pronounced and deserving of special consideration.

For example, the module 11 is approximately six times as strong as it would be if it were made of steel of comparable weight. Furthermore it is much more corrosion resistant than previously utilized materials and manifests greater thermal resistance than it would be if it were manufactured of a thermoplastic material, for example. It is much more errosion resistant than would be the case if it were made of thermoplastics, for example, asis much more rigid than a similar member made of steel or thermoplastic.

Furthermore, the module 11 is extremely light weight when compared with other materials and this enhances theretrievability of the module. For example, in operation it may be desired from time to time to raise the module. 11 above the liquid level for inspection purposes or the like. Because of the fiber glass constructon the module 11 can be lifted by means of a cable, winch or the like which may be attached to the flanges 13 and the end caps 14 by means of apertures formed therein as indicated at reference numerals 36, 36 in FIG. 5. Furthermore the module 11 may be quite long, extending feet and beyond, and suffer no substantial bowing or lagging.

The above described method of manufacture provides for maximum flexibility, since not only can the module 11 be made in any desired length but in addition any number of liquid nozzles 28 and liquid air nozzles 12 may be mounted thereon. Consequently a single cross-section configuration of the module 11 may be utilized over a wide range of capacity requirements.

The flexibility inherent in the fabrication and utilization of the multiple jet aerator module 11 may also result in the optimization of the liquid pump and air compressor which serve to pump the waste liquid and the air through the liquid and air ducts 23 and 24. In previously known jet aerator systems, it is not unusual to find that the pump and air compressors have not been selected to provide the most efficient size relationship because to do so require a substantially increased number of jet aerators. By virtue of the present invention, however, the number of liquid-air jet nozzles has little bearing on cost and as many as space permits can be accommodated. In the circumstances the liquid pumps and air compressors can now be selected to provide optimum size relationship without any real concern for the number of jet aerators which will be required in order to fully enjoy the benefits of such size relationships.

As noted above, the radius of the air duct 24 is approximately two-thirds the radius of the liquid duct 23 in the preferred embodiment. This relationship provides a tear drop design, as shown in FIG. 5, of exceptional aerodynamic qualities. For example, in the arrangement shown in FIG. 1, the two modules 11, 11 are arranged to circulate the liquid within the tank 10 in a counterclockwise direction. The purpose of this circulation, as noted above, is to maintain in suspension those settleable solids which may be in the waste liquid. The tear drop design of the module 11 as shown in FIG. 5 materially reduces the drag resistance to the liquid within the tank 10. In know-n generation systems in which a plurality of banks of individual generators are utilized it has been necessary from time to time to increase the quantity of liquid being discharged from the generators for the purpose of maintaining the velocity of the liquid at a level sufficient to avoid the settling out of solid. The drag resistance of the previously utilized the banks of individual generators is much greater than that of the modules 11 and it is therefore believed that this reduced drag resistance will insure that additional pumping energy is not required merely to overcome the drag resistance afforded by the module 11.

Other features and advantages of the present invention may be readily apparent from the foregoing description, when taken in conjunction with the accompanying drawings, and various modifications may be effected without departing from-the spirit and scope of the novel concepts disclosed herein. While such modifications might be suggested by those versed in the art, it should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as reasonable, in the scope of my contribution to the art.

I claim:

1. A multiple jet aerator module comprising a liquid duct including a tubular sheet-form member and a plurality of longitudinally spaced circumferentially aligned liquid nozzles, and an air duct including a sheet-form member mounted on said liquid duct to form a passage therebetween and including a plurality of longitudinally spaced circumferentially aligned liquid-air nozzles,

said liquid-air nozzles corresponding in number to and being disposed respectively in radial alignment with said liquid nozzles.

2. The invention as defined in claim 1 wherein said liquid duct tubular sheet-form member comprises a circumferentially continuous right-circular cylinder.

3. The invention as defined in claim 1 wherein said air duct sheet-form member comprises a right-semi circular cylinder 4. The invention as defined in claim 1 wherein said liquid and air ducts are formed of light weight filament wound reinforced fiber glass.

5. The invention as defined in claim 1 wherein said liquid nozzles are formed of molded fiber glass and bonded to said liquid duct sheet-form member.

6. The invention as defined in claim 5 wherein said liquid nozzles are bonded to said liquid duct sheet-form member by means of an epoxy resin.

7. The invention as defined in claim 1 wherein said liquid-air nozzles are formed of fiber glass and bonded to said air duct sheet-form member.

8. The invention as defined in claim 7 wherein said liquid-air nozzles are bonded to said air duct sheetform member by means of an epoxy resin.

9. The invention as defined in claim 1 wherein said liquid and air ducts together provide a tear-drop configuration in transverse cross section.

10. The invention as defined in claim 1 and including a layer of fiber glass wound in filaments and wrapped transversely around the liquid duct and the air duct mounted thereon to provide strength, rigidity and streamlining to the module.

11. The invention as defined in claim 1 wherein said liquid duct tubular sheet-form member comprises a circumferentially continuous right-circular cylinder and said air duct sheet-form member comprises a rightsemicircular cylinder, the radius of said air duct being substantially less than the radius of said liquid duct.

12. The method of making a multiple jet aerator module comprising the steps of forming a one-piece tubular shaped circumferentially continuous sheet-form fiber glass liquid duct of constant cross-sectional configuration along the length thereof, providing a plurality of longitudinally spaced circumferentially aligned bores in said liquid duct,

bonding a plurality of molded fiber glass liquid nozzles to said liquid duct in alignment respectively with said liquid duct bores, forming an elongated one-piece fiber glass sheetform member having a constant cross-sectional configuration along the length thereof different from the configuration of said liquid duct,

bonding said latter sheet-form member to said liquid duct to provide an enclosed air duct therebetween,

providing a plurality of bores in said air duct corresponding in number and location to said bores in said liquid duct, and

bonding a plurality of molded fiber glass liquid-air nozzles to said air ducts in alignment respectively with said air duct bores.

13. The invention as defined in claim 12 wherein said nozzles are bonded to their respective ducts by means of an epoxy resin.

14. The invention as defined in claim 12 and including the step of wrapping said liquid duct with the air duct bonded thereto with filament wound fiber glass to enhance the strength, rigidity and streamlining configuration of the module.

15. The method of making a multiple jet aerator module comprising the steps of forming a first right-circular tubular circumferentially continuous fiber glass sheet-form member to provide a liquid duct,

providing a plurality of longitudinally spaced circumferentially aligned bores therein,

bonding a plurality of molded fiber glass liquid nozzles to said first sheet-form member in register with said bores therein,

forming a second right-circular tubular circumferentially continuous fiber glass sheet-form member having a diameter less than the diameter of said first sheet-form member,

removing a portion of said second sheet-form member along the length thereof to provide a segmental right-circular sheet-form member, bonding said segmental right-circular sheet-form member to said first sheet-form member in parallel relation to provide an air duct therebetween,

providing a plurality of bores in said segmental rightcircular sheet-form member corresponding in number and location to said bores in said first sheetform member, and

bonding a plurality of molded fiber glass liquid-air nozzles to said segmental right-circular sheet-form member in register with said bores therein.

16. The invention as defined in claim 15 and including the step of wrapping the module with a layer of filament-wound fiber glass.

17. The invention as defined in claim 15 in which said nozzles are bonded to their respective sheet-form member by an epoxy resin. 

1. A multiple jet aerator module comprising a liquid duct including a tubular sheet-form member and a plurality of longitudinally spaced circumferentially aligned liquid nozzles, and an air duct including a sheet-form member mounted on said liquid duct to form a passage therebetween and including a plurality of longitudinally spaced circumferentially aligned liquid-air nozzles, said liquid-air nozzles corresponding in number to and being disposed respectively in radial alignment with said liquid nozzles.
 2. The invention as defined in claim 1 wherein said liquid duct tubular sheet-form member comprises a circumferentially continuous right-circular cylinder.
 3. The invention as defined in claim 1 wherein said air duct sheet-form member comprises a right-semi circular cylinder.
 4. The invention as defined in claim 1 wherein said liquid and air ducts are formed of light weight filament wound reinforced fiber glass.
 5. The invention as defined in claim 1 wherein said liquid nozzles are formed of molded fiber glass and bonded to said liquid duct sheet-form member.
 6. The invention as defined in claim 5 wherein said liquid nozzles are bonded to said liquid duct sheet-form member by means of an epoxy resin.
 7. The invention as defined in claim 1 wherein said liquid-air nozzles are formed of fiber glass and bonded to said air duct sheet-form member.
 8. The invention as defined in claim 7 wherein said liquid-air nozzles are bonded to said air duct sheet-form member by means of an epoxy resin.
 9. The invention as defined in claim 1 wherein said liquid and air ducts together provide a tear-drop configuration in transverse cross section.
 10. The invention as defined in claim 1 and including a layer of fiber glass wound in filaments and wrapped transversely around the liquid duct and the air duct mounted thereon to provide strength, rigidity and streamlining to the module.
 11. The invention as defined in claim 1 wherein said liquid duct tubular sheet-form member comprises a circumferentially continuous right-circular cylinder and said air duct sheet-form member comprises a right-semicircular cylinder, the radius of said air duct being substantially less than the radius of said liquid duct.
 12. The method of making a multiple jet aerator module comprising the steps of forming a one-piece tubular shaped circumferentially continuous sheet-form fiber glass liquid duct of constant cross-sectional configuration along the length thereof, providing a plurality of longitudinally spaced circumferentially aligned bores in said liquid duct, bonding a plurality of molded fiber glass liquid nozzles to said liquid duct in alignment respectively with said liquid duct bores, forming an elongated one-piece fiber glass sheet-form member having a constant cross-sectional configuration along the length thereof different from the configuration of said liquid duct, bonding said latter sheet-form member to said liquid duct to provide an enclosed air duct therebetween, providing a plurality of bores in said air duct corresponding in number and location to said bores in said liquid duct, and bonding a plurality of molded fiber glass liquid-air nozzles to said air ducts in alignment respectively with said air duct bores.
 13. The invention as defined in claim 12 wherein said nozzles are bonded to their respective ducts by means of an epoxy resin.
 14. The invention as defined in claim 12 and including the step of wrapping said liquid duct with the air duct bonded thereto with filament wound fiber glass to enhance the strength, rigidity and sTreamlining configuration of the module.
 15. The method of making a multiple jet aerator module comprising the steps of forming a first right-circular tubular circumferentially continuous fiber glass sheet-form member to provide a liquid duct, providing a plurality of longitudinally spaced circumferentially aligned bores therein, bonding a plurality of molded fiber glass liquid nozzles to said first sheet-form member in register with said bores therein, forming a second right-circular tubular circumferentially continuous fiber glass sheet-form member having a diameter less than the diameter of said first sheet-form member, removing a portion of said second sheet-form member along the length thereof to provide a segmental right-circular sheet-form member, bonding said segmental right-circular sheet-form member to said first sheet-form member in parallel relation to provide an air duct therebetween, providing a plurality of bores in said segmental right-circular sheet-form member corresponding in number and location to said bores in said first sheet-form member, and bonding a plurality of molded fiber glass liquid-air nozzles to said segmental right-circular sheet-form member in register with said bores therein.
 16. The invention as defined in claim 15 and including the step of wrapping the module with a layer of filament-wound fiber glass.
 17. The invention as defined in claim 15 in which said nozzles are bonded to their respective sheet-form member by an epoxy resin. 